2. Chemistry, physics, bottom-up "nanometric" processes

The main challenges are to develop techniques/methods with sufficient levels of resolution and broad compatibility with materials that can exert an influence on printability, voxel size, and consequently, constructability and spatial resolution. The most successful avenues include:

• top-down patterns involving the masking and selective removal of materials, often in repetitive sequences;

• bottom-up strategies based on assembling components or depositing materials;

• transformations of two-dimensional (2D) shapes into 3D, triggered by internal forces or external stimuli (as in the case of origami);

• assembly guided mechanically by substrate deformations (kirigamis).

Additive manufacturing can exploit nanotechnologies...